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Duct penetration through ribbed metal deck roof?Helpful Member!(3) 

mahalo (Structural) (OP)
21 Apr 07 11:18
I need to run a 24" square duct through a ribbed metal roof to an exhaust fan. I want to achieve a watertight, silent finished product. Does anyone know where I could find a section view that would show the proper way to flash this penetration?
Helpful Member!  mahalo (Structural) (OP)
21 Apr 07 17:14
Oh yeah, one other thing the roof is sloped.
Helpful Member!  berkshire (Aeronautics)
22 Apr 07 1:37
SMACNA hand book, Duct construction standards.
B.E.
mahalo (Structural) (OP)
22 Apr 07 19:52
Thanks berkshire. Got a web address for that?
berkshire (Aeronautics)
22 Apr 07 22:42
Helpful Member!  DrRTU (Mechanical)
22 Apr 07 23:11
You need to find a local curb fabricator. Your sheetmetal contactor should measure the pattern of standing seam. The curb will be built with the reverse pattern to match the roof. The roofing contractor he should be able to tell you the panel manufacture and they may have standard details like the size of the cricket on the high side. http://www.rpscurbs.com/catalogstart.htm

mahalo (Structural) (OP)
23 Apr 07 2:55
I am really grateful for y'alls feedback. what about this scenario? I match the flashing to the roof like suggested then install flashing and caulk with geocell 2300 then put a layer of epdm around it. Also, if the flashing goes under the roof on the up side does it go over the roof on the down side?
berkshire (Aeronautics)
23 Apr 07 13:37
mahalo (Structural)
The item you are referring to as flashing  should be part of your roof jack or curb. And yes it should go under on the upward side and over on the downward side.
 You need to consult with an architectural sheet metal shop, or a roofing specialist.
B.E.

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